Charging System: Description and Operation

The alternator generates an alternating current (AC) voltage in its windings as it is belt driven by the engine. The integral rectifier converts this AC voltage to direct current (DC) voltage.

The voltage regulator, a component which is included in the alternator frame, has as its primary function the control of alternator output to meet electrical system requirements. The regulator also controls the charging system indicator light and the charging signal (FR).

Fuse 22 supplies battery voltage to the charging system indicator light. With the engine not running and the ignition switch in RUN, terminal L of the alternator is grounded by the voltage regulator and the charging system indicator light. With the engine running and the alternator charging, the voltage at terminal L rises and the charging system indicator light will go out. The rise in voltage at terminal L also provides an engine running/charging system functioning signal to the integrated control unit and the ABS control unit. If the alternator fails to charge, terminal L will remain below battery voltage and the charging system indicator light will stay on.

The charging (FR) signal is supplied to the powertrain control module (PCM). The control module detects whether the alternator is charging and the charging load by evaluating changes in the charging signal. High charging demands place an increased load on the engine. To maintain a more constant idle speed, the control module compensates for the changing engine load by adjusting the idle control.